Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Income Statement Data Abstract
Net interest income	$ 187,747	$ 175,902
Net intersegment interest income	0	0
Segment net interest income	187,747	175,902
Noninterest income(a)	74,467	95,343
Total revenue	262,214	271,245
Provision for credit losses	(3,990)	(23,004)
Noninterest expense	173,292	175,347
Income before income taxes	92,912	118,903
Income tax expense (benefit)	18,650	24,602
Net income	74,262	94,301
Segment Balance Sheet Data
Allocated goodwill	1,104,992	1,104,992
Operating Segments | Corporate and Commercial Specialty
Segment Income Statement Data Abstract
Net interest income	90,633	89,661
Net intersegment interest income	8,525	4,670
Segment net interest income	99,158	94,331
Noninterest income(a)	37,790	41,828
Total revenue	136,948	136,160
Provision for credit losses	12,653	16,680
Noninterest expense	56,559	55,448
Income before income taxes	67,736	64,032
Income tax expense (benefit)	12,313	11,891
Net income	55,423	52,141
Segment Balance Sheet Data
Allocated goodwill	525,836	525,836
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income	69,544	71,775
Net intersegment interest income	18,833	14,889
Segment net interest income	88,377	86,664
Noninterest income(a)	33,207	47,331
Total revenue	121,584	133,995
Provision for credit losses	4,656	5,928
Noninterest expense	98,660	100,353
Income before income taxes	18,267	27,714
Income tax expense (benefit)	3,836	5,820
Net income	14,431	21,894
Segment Balance Sheet Data
Allocated goodwill	579,156	579,156
Operating Segments | Risk Management and Shared Services
Segment Income Statement Data Abstract
Net interest income	27,570	14,465
Net intersegment interest income	(27,358)	(19,559)
Segment net interest income	212	(5,094)
Noninterest income(a)	3,470	6,184
Total revenue	3,683	1,091
Provision for credit losses	(21,300)	(45,612)
Noninterest expense	18,073	19,546
Income before income taxes	6,909	27,156
Income tax expense (benefit)	2,501	6,890
Net income	4,409	20,266
Segment Balance Sheet Data
Allocated goodwill	$ 0	$ 0